1. Technical Field
This invention relates to joints for rotating members and, more particularly, structural pivots.
2. Discussion
Structural pivots are often used to overcome many of the disadvantages associated with other types of rotating joints such as knife edges, bearings, ball and socket joints and the like. Among the advantages of structural pivots is the elimination of friction, backlash, wear, the lack of requirement for lubrication, insensitivity to contamination, and the ability to operate over a wide range of environmental conditions. Structural pivots can be used in a wide variety of applications such as in gimbal ring mounts, pressure transducers, throttle linkages and automatic bag fillers. They are also finding increasing application in optical systems for mounting oscillating mirrors and the like.
One of the best known commercially available structural pivots is the "Free-Flex" pivot marketed by the Electric and Fluid Power Division of The Bendix Corporation. The construction of the Free-Flex pivot is described in the trade literature and in a paper by Troeger, "Considerations in the Application of Flexural Pivots", Automatic Control Data Systems Engineering Volume 17, No. 4, November, 1962. Despite its several advantages, the Free-Flex design also has its share of disadvantages. One particular drawback is that the geometric center of its rotating member will shift as the member is angularly deflected. As a result, its use in several applications like the above-mentioned precision optical systems is limited unless special precautions are taken.
Those skilled in the art have not been satisfied with leaving the state of pivot technology unimproved. Pivots that have been designed after the Free-Flex pivot include the pivots disclosed in U.S. Pat. No. 4,405,184, to Bahiman, entitled "Unidirectional Flexural Pivot," and disclosed in U.S. Pat. No. 4,802,784, to Brooks, entitled "Bi-Flex Pivot," and disclosed in U.S. Pat. No. 4,812,072, also to Brooks, entitled "Torsion Structural Pivot." A distinct disadvantage of the Bahiman pivot, which utilizes only flexural action in its flexible elements, is that it will rotate in only one direction. The Brooks pivots will rotate in both directions and substantially eliminate the geometric center shift of its rotating members, that was a disadvantage of the Free-Flex pivot. However, the Brooks pivots both utilize only one type of motion, either flexural or torsional respectively. While the Brooks pivots represent an improvement over both the Free-Flex and Unidirectional Flexural pivots, it would still be desirable to improve upon the Brooks pivots by increasing pivot reliability, extending pivot life, reducing pivot stress and non-linearity, and increasing pivot strength or rotation angle range.